The present invention relates to a multi-piece golf ball having a core and three or more cover layers. More specifically, the invention relates to a multi-piece solid golf ball which has a high initial velocity on shots taken with a driver.
Numerous golf balls with multilayer covers have hitherto been disclosed. For example, various golf balls with multilayer covers are described in U.S. Pat. Nos. 5,833,553, 6,126,559, 6,220,972, 6,561,928, 6,309,314 and 6,585,608. However, these prior-art golf balls do not have a sufficient initial ball velocity on shots taken with a driver.
In the golf balls with multilayer covers disclosed in U.S. Pat. Nos. 5,779,562, 6,117,025, 6,152,834, 6,394,914, 6,213,895 and 6,994,638, the hardness relationships within the multilayer cover have been optimized. Yet, it has been difficult to achieve a sufficiently high initial ball velocity on shots taken with a driver, particularly on shots taken with a driver at a high head speed.
Up until now, golf balls obtained by using a conventional ionomer resin to form the innermost cover layer which directly encases the core have not had a good rebound. To compensate, one known approach has been to reduce the spin rate by increasing the thickness of the inner cover layer made of ionomer resin. Unfortunately, this only lowers the rebound. Moreover, increasing the core deflection in order to soften the feel of the ball on shots taken with a driver also lowers the ball rebound.
The use of highly neutralized ionomer resins as golf ball cover materials is known to the art, but such covers are relatively thin. Although the golf balls obtained in such cases do have an improved rebound compared with golf balls obtained using prior-art ionomer resins, the spin rate-lowering effect on shots taken with a driver has been rather negligible.